Nigel Perry asks whether it is possible to make trumpet pipes with
harmonium reeds.  A harmonium reed is a free reed, that is, the reed
vibrates within its metal frame without touching it.  Similar types of
reeds are used in American organs and organettes.  The main difference
is that harmoniums blow and American organs suck.

Fairground organ trumpets use beating reeds, where the reed oscillates
against the shallot.  The reed is tuned with the tuning wire, which
holds the reed against the shallot, and by moving the wire along the
length of the reed changes its effective length and hence the pitch.

In general, beating reeds are used for louder instruments, and free
reeds usually speak into shaped cavities rather than trumpet
resonators.  There is, however, no reason why a free reed cannot be
used with a trumpet resonator, either as a fixed frequency free reed
or with a tuning wire.

Historically, there is a precedent for using free reed trumpets in
indoor instruments.  They were used by the great orchestrion makers,
Welte and Imhof.

Nicholas Simons, England